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How and why to take a logarithm of an image [video]

175 points by jgwil2

by boriskourt

3 subcomments

by rappatic

1 subcomments

Similarly, it's possible to take the derivative of a song. You can use a Fourier transform to express the song's waveform as a series of sin and cosine functions, then take the derivative.
Imagine, for the sake of simplicity, you could express the song's waveform with the function 13 * sin(41x).
The derivative of this function is 533 * cos(41x).
Cosine, of course, is just a phase shifted sine, and the constant coefficient inside the function stays the same. So you're not changing anything about the shape of the wave, just stretching it vertically.
This has the effect of mimicking a "high pass filter," amplifying the volume of the highs.

by m-hodges

4 subcomments

The title I get when I click on this is, "How (and why) to take a logarithm of an image"

by OscarCunningham

1 subcomments

I've been wondering if you could do a similar thing for a Droste effect image containing two copies of itself. Packs of Laughing Cow cheese show a cow with two earrings, each of which is a pack of the cheese.

by pierrec

1 subcomments

This kind of technique can be used in 3D space as well! The analysis here represents Escher's techniques as conformal maps in the complex plane. Conformal maps are also possible, though more limited, in R^3. This is something that I explored some years ago and wrote an article about it, though it focuses more on graphics than math: https://www.osar.fr/notes/logspherical/

by aprentic

0 subcomment

Those videos are awesome! 3B1Bs visualizations finally made e^(pi*i) make sense.
His videos on Euler's formula inspired me to make a silly toy so I could play with it myself.
https://gitlab.com/aprentic/complex-viz/

by Jeff_Brown

6 subcomments

I love 3B1B but generally don't have time to watch long videos. Can anyone sum up the punchline?

by toxik

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So in other words you can take any Droste image and make an Escher zooming spiral effect. Neat.
Also curious what happens if you take Escher's painting and undo the effect. Probably not great since it wasn't in the video.
What a cool video.

by amelius

0 subcomment

by manudaro

1 subcomments

I've been loking into how 3B1B builds their rendering pipeline, and it's honestly mind blowing. They use Python along with custom OpenGl shaders to handle most of geometric transformations, shich seems to be what creates those "brain breaking" visual effects.It's fascinating how our visual cortex tries to interpret overlapping geometric patterns and ends up producing such counterintuitive perceptions. Shat I still can't quite wrap my hand around is... to what extent are these effects caused by the rendering itself, and how much of it is just how our brain interprets the visual information?

by qoez

1 subcomments

Makes me wonder how this would look/feel interactively if a game world was rendered like this

by coldpie

4 subcomments